Memphis played a significant religious role in ancient Egypt as the home of Ptah, a patron of craftsmen and creator god, whose great temple was a prominent structure in the city. According to the "Memphite Theology," Ptah created humans through the power of his heart and speech, demonstrating the philosophical sophistication of Memphis’s priests. Certain coronation ceremonies and the Heb-Sed festival, which possibly reenacted the unification of Egypt and was celebrated by a king after 30 years of rule and every three years thereafter, were traditionally held in Memphis. Even after the rise of the god Amon of Thebes, Ptah remained a principal god, and kings continually added to the temple of Ptah . Amenhotep III’s son, Akhenaten, even built a temple to his god, Aten, in Memphis. The Serapeum, dedicated to the cult of Apis, was also constructed in Memphis.